| dc.description.abstract | A study to determine the effect of varying soybean planting density on maize and soybean yields
in maize-soybean intercrops was carried out in Butere and Mumias districts of western Kenya
during the short and long rain growing seasons of 2011 and 2012 respectively. To identify the
predominant crops and understand the associated production practices in the smallholder fanning
system a survey was carried out. Field experiments were laid out in a Randomized Complete
Block Design (RCBD) with a factorial arrangement replicated three times. Three maize: soybean
planting densities 1:1(Dl), 1:2 (D2) and 1:3(D3), representing rows of maize and soybean
respectively, were tested. Three soybean varieties: NAMSOY 4m, SC SQUIRE and TGx 1987-
18F intercropped with imidazolinone- resistant (IR) maize were grown with sole soybean (D4)
and sole maize (SM) included as controls. At harvest of the intercrops, soil pH, total Nand
available P were assessed followed by maize rotation trial. Above and below ground biomass of
soybean, nitrogen fixation, grain and dry matter yields of maize and soybean and land equivalent
ratio were also measured. At completion of the study analyses of the economic analyses, net
benefit, incremental net benefit and benefit cost ratio of the intercrop and rotation trials were
carried out. The survey revealed low planting densities of legumes in the maize-legume intercrop
system (1: 1 and 1:2) which is the predominant practice in Butere and Mumias districts of
western Kenya. Fanners also adopted legumes cereal rotation but the population of legumes in
the preceding season was low, hence its benefits; on subsequent maize crop were not fully
exploited. Besides beans, fanners were growint:s.P'Ybeans due to their high nutritive value and
selling price. Higher above and below ground biomass and N accumulation in the intercrops
were recorded in D3 for soybean variety TGx 1987-18F. The D3 for variety SC SQUIRE
recorded high soybean grain and dry matter yields. Maize grain and dry matter yields were
significantly different across planting densities with .01 recoding higher yields. Land equivalent
ratio of the intercrops in the short rains season was higher in D2 for soybean variety SC SQUIRE
and in the long rains season in D3 for same variety. No significant differences were detected on
soil pH, total N and available P before the experimental setup and after harvest of the intercrops.
Maize succeeding D3 for soybean variety TGx 1?87 -18F recorded the highest grain and dry
matter yields. The D3 for soybean variety SC SQUIRE succeeded by maize recorded the highest
net benefit and benefit cost ratio. From the results of the study it was concluded that maizesoybean
intercrops with high soybean population should be planted during the short rains season
and rotated with maize in the long rains season. Planting density D3 for soybean variety SC
SQUIRE is the recommended technology to improve soybean biomass production and N
accumulation, increase yield of subsequent maize and provide high cash incomes to the
smallholder fanners. However, D2 for soybean variety SC SQUIRE is also an attractive option
as it provides high yields of both maize and soybean. A similar study involving control plots of
sole maize and soybean in same plant populations as in the different intercrops is recommended
for better comparison and evaluation of the effectiveness of the-intercrops.
Key words: Intercropping, rotation, planting densities, biomass· and N accumulation, land
equivalent ratio, residues incorporation, economic returns. | en |
